Light-emitting device and electronic apparatus

ABSTRACT

A light-emitting device includes a power feeding line to which a predetermined voltage is supplied; a light-emitting element formed of a first electrode, a second electrode, and a light-emitting layer interposed between the first electrode and the second electrode; and a driving transistor that controls the amount of current supplied to the light-emitting element from the power feeding line. The power feeding line includes a portion interposed between the first electrode and the driving transistor.

This application is a continuation of U.S. patent application Ser. No.11/624,844 which was filed on Jan. 19, 2007 now U.S. Pat. No. 7,872,264and claims priority to Japanese Application Nos. 2006-015370, filed Jan.24, 2006 and 2006-289587, filed Oct. 25, 2006. The entire disclosures ofthe prior applications are hereby incorporated herein by reference intheir entirety.

BACKGROUND

1. Technical Field

The invention relates to configurations of light-emitting devices inwhich light-emitting materials, such as electroluminescent (EL)materials, are used.

2. Related Art

Active-matrix light-emitting devices, in which a transistor is providedin association with each light-emitting element to control the amount ofcurrent supplied to the light-emitting element, have been proposed(e.g., JP-A-2004-119219). In this type of light-emitting device, forexample, in order to improve the numerical aperture (the ratio ofregions where light is actually emitted from light-emitting elements tothe region where the light-emitting elements are arrayed), layers oftransistors and light-emitting elements, and lines for electricallyinterconnecting these elements are laminated on a substrate.

In the configuration where the elements are laminated as describedabove, however, capacitive coupling occurs between elements that arelocated in proximity to each other. That is, stray capacitances couldarise between such elements. For example, when the waveforms of varioussignals are rounded due to stray capacitors of various elements,accurate control of light-emitting elements could be inhibited.

SUMMARY

An advantage of some aspects of the invention is that the effects ofstray capacitances associated with various elements of a light-emittingdevice can be reduced.

According to a first aspect of the invention, there is provided alight-emitting device including a light-emitting element formed of afirst electrode, a second electrode, and a light-emitting layerinterposed between the first electrode and the second electrode; adriving transistor that controls the amount of current supplied to thelight-emitting element; and a capacitor (e.g., a capacitor C1 shown inFIG. 2 or a capacitor C2 shown in FIG. 21 or FIG. 32) electricallyconnected to a gate electrode of the driving transistor. The firstelectrode overlaps the capacitor.

In the light-emitting device described above, since the first electrodeis formed so as to overlap the capacitor, it is readily possible toallocate an area for the first electrode without forming the firstelectrode so as to overlap various switching elements used to controlthe light-emitting element. Therefore, it is possible to reduce a straycapacitance between the first electrode and the switching elements, andtherefore to prevent delay in switching operations attributable to thestray capacitance, while allocating a sufficient area for the firstelectrode.

For example, a selecting transistor (e.g., a selecting transistor Ts1shown in FIG. 2 or FIG. 21) that is turned on or off according to aselection signal is provided, and a gate electrode of the drivingtransistor is pulled to a potential corresponding to a data signalsupplied through a data line via the selecting transistor when theselecting transistor is turned on. In this case, the first electrode isformed so as not to overlap the selecting transistor. According to thisconfiguration, the stray capacitance between the first electrode and theselecting transistor is reduced. Accordingly, high-speed operation ofthe selecting transistor is allowed (i.e., delay attributable to thestray capacitance can be prevented).

As another example, an initializing transistor (e.g., an initializingtransistor Tint shown in FIG. 2) that is turned on or off according toan initialization signal is provided, and a gate electrode and a drainelectrode of the driving transistor are electrically connected to eachother via the initializing transistor when the initializing transistoris turned on. In this case, the first electrode is formed so as not tooverlap the initializing transistor. According to this configuration,the stray capacitance between the first electrode and the initializingtransistor is reduced. Accordingly, high-speed operation of theinitializing transistor is allowed. The gate electrode of the drivingtransistor electrically connected via the initializing transistor ispulled to a potential corresponding to a threshold voltage of thedriving transistor. Thus, it is possible to compensate for an error ofthe threshold voltage of the driving transistor.

The capacitor is typically used to set or maintain a gate voltage of thedriving transistor. In an example configuration, the capacitor (e.g.,the capacitor C1 shown in FIG. 2) is located between the gate electrodeof the driving transistor and the data line. In this configuration, thegate electrode of the driving transistor is pulled to a potentialcorresponding to an amount of change in the potential of the data line.In another example configuration, the capacitor (e.g., the capacitor C2shown in FIG. 21 or FIG. 32) is located between the gate electrode ofthe driving transistor and a line (e.g., a power supply line) throughwhich a constant voltage is supplied. In this configuration, a voltagesupplied from the data line to the gate electrode of the drivingtransistor is maintained by the capacitor.

According to a second aspect of the invention, there is provided alight-emitting device including a power feeding line (e.g., a powersupply line 15 shown in FIG. 2 or FIG. 21) through which a predeterminedvoltage is supplied; a light-emitting element formed of a firstelectrode, a second electrode, and a light-emitting layer interposedbetween the first electrode and the second electrode; and a drivingtransistor that controls the amount of current supplied to thelight-emitting element through the power feeding line. The power feedingline is typically a power supply line for supplying a power supplyvoltage.

In this configuration, the power feeding line exists between the firstelectrode and the driving transistor. Therefore, compared with aconfiguration where a conductor does not exist between the firstelectrode and the driving transistor, capacitive coupling between theseelements is suppressed. Accordingly, the effect of change in thepotential of one of the first electrode and the driving transistor onthe potential of other can be alleviated.

According to a third aspect of the invention, there is provided alight-emitting device including a data line through which a data signalis supplied, a power feeding line through which a predetermined voltageis supplied; a light-emitting element formed of a first electrode, asecond electrode, and a light-emitting layer interposed between thefirst electrode and the second electrode; and a driving transistor thatcontrols the amount of current supplied to the light-emitting elementthrough the power feeding line according to the data signal. The powerfeeding line includes a portion interposed between the first electrodeand the driving transistor. In this configuration, the power feedingline exists between the first electrode and the data line. Therefore,compared with a configuration where a conductor does not exist betweenthe first electrode and the data line, capacitive coupling between theseelements is suppressed. Accordingly, the effect of change in thepotential of one of the first electrode and the data line on thepotential of other can be alleviated.

According to a fourth aspect of the invention, there is provided alight-emitting device including a data line through which a data signalis supplied, a light-emitting element formed of a first electrode, asecond electrode, and a light-emitting layer interposed between thefirst electrode and the second electrode; and a driving transistor thatcontrols the amount of current supplied to the light-emitting elementaccording to the data signal. The first electrode is a light-reflectingelectrode formed on a surface of an insulating layer (e.g., a firstinsulating layer L1 or a second insulating layer L2 shown in FIG. 11)covering the data line, and a periphery thereof overlaps the data line.

In this configuration, by making variation in height on the surface ofthe insulating layer so as to reflect the thickness of the data line, itis possible to form an inclined surface (e.g., an inclined surface 211shown in FIG. 11) in the proximity of the periphery of the firstelectrode. The efficiency of usage of light can be improved by causinglight emitted from the light-emitting layer to be reflected on theinclined surface.

According to a fifth aspect of the invention, there is provided alight-emitting device including a light-emitting element formed of afirst electrode, a second electrode, and a light-emitting layerinterposed between the first electrode and the second electrode; adriving transistor that controls the amount of current supplied to thelight-emitting element; a capacitor electrically connected to a gateelectrode of the driving transistor; and an auxiliary line electricallyconnected to the second electrode, the auxiliary line being formed of amaterial having a resistivity lower than a resistivity of a material ofthe second electrode. The auxiliary line does not overlap the drivingtransistor or the capacitor.

In this configuration, since the auxiliary line is formed so as not tooverlap the driving transistor or the capacitor, the stray capacitancebetween the auxiliary line and the driving transistor or between theauxiliary line and the capacitor is reduced. Therefore, the effect ofchange in the potential of one of the auxiliary line and the drivingtransistor (or the capacitor) on the potential of the other can bealleviated.

In the light-emitting device according to the fifth aspect, for example,a selecting transistor that is turned on or off according to a selectionsignal, and an insulating layer (e.g., a wall 25 shown in FIG. 4)overlapping the selecting transistor and having an aperture (e.g., anaperture 251 shown in FIG. 4) are provided. In this case, the drivingtransistor controls the amount of current supplied to the light-emittingelement according to a data signal supplied through a data line via theselecting transistor when the selecting transistor is turned on. In thisconfiguration, the auxiliary line can be formed suitably above theinsulating layer. In this configuration, the insulating layer existsbetween the auxiliary line and the selecting transistor. Thus,capacitive coupling between the auxiliary line and the selectingtransistor is suppressed. In order to allocate sufficient areas for apower supply line and an aperture through which the light-emittingelement emits light, preferably, the selecting transistor is formed soas to overlap the auxiliary line.

In another example, an initializing transistor that is turned on or offaccording to an initialization signal, an insulating layer overlappingthe initializing transistor and having an aperture are provided. Also inthis configuration, the auxiliary line can be formed suitably above theinsulating layer. According to this configuration, capacitive couplingbetween the auxiliary line and the initializing transistor issuppressed. In order to allocate sufficient areas for a power supplyline and an aperture through which the light-emitting element emitslight, preferably, the initializing transistor is formed so as tooverlap the auxiliary line.

According to a sixth aspect of the invention, there is provided alight-emitting device including a plurality of control lines extendingin a first direction (e.g., an X direction in FIGS. 18 to 20 or FIGS. 28to 30); a data line extending in a second direction (e.g., a Y directionin FIGS. 18 to 20 or FIGS. 28 to 30) and crossing the plurality ofcontrol lines, the second direction being different from the firstdirection; and a plurality of unit elements arrayed in the seconddirection and located at positions corresponding to intersectionsbetween the plurality of control lines and the data line. Each of theplurality of unit elements includes a light-emitting element formed of afirst electrode, a second electrode, and a light-emitting layerinterposed between the first electrode and the second electrode; adriving transistor that controls the amount of current supplied to thelight-emitting element according to a potential of a gate electrode ofthe driving transistor, the potential of the gate electrode being setaccording to a signal supplied through the data line; and a controltransistor that controls whether or not a predetermined voltage is to besupplied to the gate electrode of the driving transistor or whether ornot a current is to be supplied to the light-emitting element, accordingto a signal supplied through a control line associated with the unitelement among the plurality of control lines. The control transistorthat controls whether or not to supply a predetermined voltage to thegate electrode of the driving transistor corresponds to, for example, aselecting transistor Ts1 or an initializing transistor Tint shown inFIG. 2. The control transistor that controls whether or not to supply acurrent to the light-emitting element corresponds to, for example, alight-emission controlling transistor Tcnt shown in FIG. 31. Thus, thecontrol line in this aspect corresponds to, for example, a selectingline 11 or an initializing line 12 shown in FIG. 2 or a light-emissioncontrolling line 14 shown in FIG. 31.

In this configuration, in a first unit element (e.g., a unit element Pon an i-th row in FIGS. 18 to 20 or FIGS. 28 to 30) among the pluralityof unit elements, the control transistor and the control line arelocated on a first side of the driving transistor in the seconddirection. On the other hand, in a second unit element (e.g., a unitelement P on an (i−1)-th row) and a third unit element (e.g., a unitelement P on an (i+1)-th row) among the plurality of unit elements, thesecond unit element being adjacent to the first unit element on thefirst side in the second direction and the third unit element beingadjacent to the first unit element on a second side in the seconddirection, the control transistor and the control line are located onthe second side of the driving transistor in the second direction. Thedata line includes a plurality of first data-line portions and a seconddata-line portions, the plurality of first data-line portions beingformed out of the same layer as the plurality of control lines andarrayed in the second direction, and the second data-line portion beingformed on a surface of an insulating layer covering the plurality ofcontrol lines and electrically interconnecting the plurality of firstdata-line portions. The first data-line portions are formed contiguouslyin association with the first unit element and the third unit element,and the second data-line portion crosses the control line associatedwith the first unit element and the control line associated with thesecond unit element.

According to this configuration, since the first data-line portions areformed contiguously in association with the first unit element and thethird unit element, the second data-line portion need not be formed inthe space between the first unit element and the third unit element. Inthis specification, when a plurality of elements is formed in the sameprocess by selective removal of a common film (regardless of whether thefilm is a single-layer film or a multi-layer film), the plurality ofelements will be described as “formed out of the same layer”, regardlessof whether the elements are formed contiguously or separately. Specificexamples of the sixth aspect described above will be described later asthird and fifth embodiments.

In the light-emitting device according to the sixth aspect, for example,a power feeding line through which a predetermined voltage is suppliedis provided, and the driving transistor controls the amount of currentsupplied to the light-emitting element through the power feeding line.The power feeding line is formed out of the same layer as the seconddata-line portions of the data line, and the power feeding line includesa portion (e.g., a connecting portion 153 shown in FIG. 29) of the firstdata-line portion, the portion of the first data-line portion beinglocated in a space between the first unit element and the third unitelement. According to this configuration, since the portion locatedbetween the first unit element and the third unit element is included,it is possible to reduce the resistance of the power feeding line.

In a more preferable configuration, an auxiliary line electricallyconnected to the second electrode, formed of a material having aresistivity lower than a resistivity of a material of the secondelectrode, is provided. The auxiliary line is formed so as to overlapthe control transistor and the control line of the first unit elementand the control transistor and the control line of the second unitelement, and is not formed in a space between the first unit element andthe third unit element. According to this configuration, compared with aconfiguration where auxiliary lines are formed in association withindividual unit elements, the width of the auxiliary line formed betweenthe first unit element and the second unit element can be increased. Inthis configuration, high precision is not required in the formation ofthe auxiliary line. Therefore, the auxiliary line can be formed bylow-cost techniques. Furthermore, since the number of auxiliary lineformed in the light-emitting device is small, margin areas providedbetween individual auxiliary lines and other elements can be reduced.Accordingly, it is possible to allocate larger areas for the auxiliarylines or light-emitting regions of light-emitting elements.

The light-emitting devices according to these aspects of the inventioncan be used in various electronic apparatuses. A typical example of suchan electronic apparatus is an apparatus including one of thelight-emitting devices as a display, such as a personal computer or acellular phone. However, applications of the light-emitting devices arenot limited to image display. For example, the light-emitting devicescan be used in an exposure apparatus (exposure head) for forming alatent image on an image carrier, such as a photosensitive drum, byradiation of light, an apparatus provided at the back of a liquidcrystal apparatus to emit light (backlight), or various illuminatingapparatuses, such as an apparatus mounted in an image reader such as ascanner to cast light on a document.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a block diagram showing an array of a plurality of unitelements in a light-emitting device according to a first embodiment.

FIG. 2 is a circuit diagram showing an electrical configuration of eachunit element.

FIG. 3 is a plan view showing a configuration of a unit element in thefirst embodiment.

FIG. 4 is a sectional view taken along a line IV-IV in FIG. 3.

FIG. 5 is a plan view showing a phase where a gate insulating layer hasbeen formed.

FIG. 6 is a plan view showing a phase where a first insulating layer hasbeen formed.

FIG. 7 is a plan view showing a phase where a second insulating layerhas been formed.

FIG. 8 is a plan view showing a plurality of unit element in a phasewhere the first insulating layer has been formed.

FIG. 9 is a plan view showing a plurality of unit element in a phasewhere the second insulating layer has been formed.

FIG. 10 is a plan view showing a plurality of unit element in a phasewhere a second electrode has been formed.

FIG. 11 is a sectional view taken along a line XI-XI in FIG. 3.

FIG. 12 is a plan view showing a configuration of a unit element in asecond embodiment.

FIG. 13 is a plan view showing a phase where a gate insulating layer hasbeen formed.

FIG. 14 is a plan view showing a phase where a first insulating layerhas been formed.

FIG. 15 is a plan view showing a phase where a second insulating layerhas been formed.

FIG. 16 is a plan view showing a plurality of unit elements in a phasewhere the second insulating layer has been formed.

FIG. 17 is a plan view showing a plurality of unit elements in a phasewhere a second electrode has been formed.

FIG. 18 is a plan view showing a plurality of unit elements in a phasewhere the first insulating layer has been formed in a third embodiment.

FIG. 19 is a plan view showing a unit element in a phase where a secondinsulating layer has been formed.

FIG. 20 is a plan view showing a unit element in a phase where a secondelectrode has been formed.

FIG. 21 is a circuit diagram showing an electrical configuration of eachunit element in a fourth embodiment.

FIG. 22 is a plan view showing a configuration of a unit element.

FIG. 23 is a plan view showing a phase where a gate insulating layer hasbeen formed.

FIG. 24 is a plan view showing a phase where a first insulating layerhas been formed.

FIG. 25 is a plan view showing a phase where a second insulating layerhas been formed.

FIG. 26 is a plan view showing a plurality of unit elements in the phasewhere the second insulating layer has been formed.

FIG. 27 is a plan view showing a plurality of unit elements in a phasewhere a second electrode has been formed.

FIG. 28 is a plan view showing a plurality of unit elements in a phasewhere a first insulating layer has been formed in a fifth embodiment.

FIG. 29 is a plan view showing a plurality of unit elements in a phasewhere a second insulating layer has been formed.

FIG. 30 is a plan view showing a plurality of unit elements in a phasewhere a second electrode has been formed.

FIG. 31 is a circuit diagram showing a configuration of a unit elementaccording to a modification.

FIG. 32 is a circuit diagram showing a configuration of a unit elementaccording to a modification.

FIG. 33 is a perspective view of a personal computer, which is anexample of an electronic apparatus according to the invention.

FIG. 34 is a perspective view of a cellular phone, which is an exampleof an electronic apparatus according to of the invention.

FIG. 35 is a perspective view of a portable information terminal, whichis an example of an electronic apparatus according to the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS A: First Embodiment A-1: ElectricalConfiguration of Light-Emitting Device

FIG. 1 is a block diagram showing the electrical configuration of alight-emitting device D according to a first embodiment of theinvention. As shown in FIG. 1, the light-emitting device D includes aplurality of selecting lines 11, a plurality of initializing lines 12,and a plurality of data lines 13. Each of the selecting lines 11 andeach of the initializing lines 12 extends in an X direction. Each of thedata lines 13 extends in a Y direction, which is perpendicular to the Xdirection. At each intersection of a pair of a selecting line 11 and aninitializing line 12 with a data line 13, a unit element (pixel) P isprovided. Thus, unit elements P are arrayed in the X and Y directions toform a matrix. Each unit element P is a minimum unit for light emission.Each unit element P receives a high-side power supply voltage Vdd via apower supply line 15.

FIG. 2 is a circuit diagram showing the configuration of each unitelement P. As shown in FIG. 2, on a path extending from the power supplyline 15 to a ground line (which is at a ground potential Gnd), alight-emitting element E and a driving transistor Tdr are provided. Thelight-emitting element E is formed of a first electrode 21 (anode), asecond electrode 22 (cathode), and a light-emitting layer 23 interposedbetween the first electrode 21 and the second electrode 22. Thelight-emitting layer 23 is composed at least of an organic EL material.The first electrodes 21 of individual unit elements P are formedseparately from each other. On the other hand, the second electrodes 22are formed contiguously in association with a plurality of unit elementsP and are connected to ground (Gnd). The light-emitting layer 23 emitsan amount of light corresponding to an amount of current that flows fromthe first electrode 21 to the second electrode 22.

The driving transistor Tdr is a p-channel thin-film transistor forcontrolling the amount of current supplied to the light-emitting elementE according to a potential Vg at a gate electrode of the drivingtransistor Tdr (hereinafter referred to as a “gate potential”). Thedriving transistor Tdr has a source electrode (S) connected to the powersupply line 15, and a drain electrode (D) connected to the firstelectrode 21 of the light-emitting element E.

Between the gate electrode and the drain electrode (the first electrode21 of the light-emitting element E) of the driving transistor Tdr, ann-channel transistor Tint for controlling the electrical connectionbetween these electrodes (hereinafter referred to as an “initializingtransistor”) is provided. The initializing transistor Tint has a gateelectrode connected to the initializing line 12. The initializing line12 receives an initializing signal Sb from a driving circuit (notshown). When the initializing signal Sb is pulled to an active level sothat the initializing transistor Tint is turned on, the gate electrodeand the drain electrode of the driving transistor Tdr are electricallyconnected to each other (a diode connection is formed). In the followingdescription, a term “diode connection” is sometimes used to describe thestate of the driving transistor Tdr where the gate electrode and thedrain electrode of the driving transistor Tdr are electrically connectedto each other via the initializing transistor Tint that has been turnedon.

As shown in FIG. 2, the unit element P includes a capacitor C1 formed ofan electrode E1 and an electrode E2. The electrode E1 is connected tothe gate electrode of the driving transistor Tdr. Between the electrodeE2 and the data line 13, an n-channel transistor Ts1 for controlling theelectrical connection between the electrode E2 and the data line 13(hereinafter referred to as a “selecting transistor”) is provided. Theselecting transistor Ts1 has a gate electrode connected to the selectingline 11. The selecting line 11 receives a selecting signal Sa from adriving circuit (not shown). The conductivity types of the drivingtransistor Tdr, the selecting transistor Ts1, and the initializingtransistor Tint may be changed as appropriate from those in the exampleshown in FIG. 2.

Next, the operation of a single unit element P will be describedregarding an initializing period, a writing period, and a drivingperiod. First, in the initializing period, a predetermined voltage Vrefis supplied from a driving circuit (not shown) to the data line 13, andthe selecting signal Sa on the selecting line 11 and the initializingsignal Sb on the initializing line 12 are maintained at an active level(high level). Thus, the voltage Vref is supplied from the data line 13to the electrode E2 of the capacitor C1 via the selecting transistorTs1. Furthermore, the initializing transistor Tint is turned on, wherebya diode connection is formed in the driving transistor Tdr. Thus, thegate potential Vg of the driving transistor Tdr converges to adifference between the power supply voltage Vdd supplied to the powersupply line 15 and a threshold voltage Vth of the driving transistor Tdr(Vg=Vdd−Vth).

When the initializing period has been finished, in the writing period,the initializing signal Sb changes to a non-active level (low level).Thus, the initializing transistor Tint is turned off, whereby the diodeconnection of the driving transistor Tdr is deactivated. Furthermore,with the selecting transistor Ts1 kept turned on, the voltage suppliedfrom the data line 13 to the electrode E2 changes from the voltage Vrefto a data voltage Vdata. The data voltage Vdata is a voltagecorresponding to a tone specified for the unit element P.

Since the impedance at the gate electrode of the driving transistor Tdris sufficiently high, when the potential at the electrode E2 changesfrom the voltage Vref to the data voltage Vdata by an amount of changeΔV (=Vref−Vdata), by capacitive coupling in the capacitor C1, thepotential at the electrode E1 changes from the potential Vg (=Vdd−Vth)set in the initializing period. The amount of change in the potential atthe electrode E1 at this time is determined in accordance with thecapacitance ratio between the capacitor C1 and stray capacitors (e.g., agate capacitance of the driving transistor Tdr and stray capacitors onother lines). More specifically, the amount of change in the potentialat the electrode E1 can be expressed as ΔV·C/(C+Cs), where C denotes thecapacitance of the capacitor C1 and Cs denotes the capacitance of thestray capacitors. Thus, at the end of the writing period, the gatepotential Vg of the driving transistor Tdr is set to a level accordingto equation (1) below:Vg=Vdd−Vth−k·ΔV  (1)where k=C/(C+Cs).

When the writing period has been finished, in the driving period, theselecting signal Sa changes to a non-active level, whereby the selectingtransistor Ts1 is turned off. Then, a current corresponding to the gatepotential Vg of the driving transistor Tdr is supplied from the powersupply line 15 to the light-emitting element E via the source electrodeand the drain electrode of the driving transistor Tdr. In response tothe current supplied, the light-emitting element E emits an amount oflight corresponding to the data voltage Vdata.

Now, assuming that the driving transistor Tdr operates in a saturatedregion, the amount of current I supplied to the light-emitting element Ein the driving period can be expressed by equation (2) below, where βdenotes a gain factor of the driving transistor Tdr, and Vgs denotes avoltage between the gate and source of the driving transistor Tdr:

$\begin{matrix}\begin{matrix}{I = {\left( {\beta/2} \right)\mspace{11mu}\left( {{Vgs} - {Vth}} \right)^{2}}} \\{= {\left( {\beta/2} \right)\mspace{11mu}\left( {{Vdd} - {Vg} - {Vth}} \right)^{2}}}\end{matrix} & (2)\end{matrix}$By assigning equation (1), equation (2) can be rewritten as follows:I=(β/2)(k·ΔV)²As understood from the above equation, the amount of current I suppliedto the light-emitting element E does not depend on the threshold voltageVth of the driving transistor Tdr. Thus, according to this embodiment,errors in the amounts of light emitted by the individual light-emittingelements E (variation in luminance) due to variation in the thresholdvoltages Vth of the individual driving transistors Tdr (deviation fromdesigned values or differences with the driving transistors Tdr of otherunit elements P) can be suppressed.

A-2: Configuration of Unit Element P

Next, a specific configuration of the unit element P will be described.FIG. 3 is a plan view showing the configuration of a unit element P, andFIG. 4 is a sectional view taken along a line IV-IV in FIG. 3. AlthoughFIG. 3 is a plan view, in order to facilitate recognition of individualelements, elements corresponding to those shown in FIG. 4 are hatched asin FIG. 4 as appropriate. This similarly applies to other plan viewsthat are referred to in the following description. Furthermore, in thefigures that are referred to in the following description, for theconvenience of description, the dimensions and ratios of individualelements are varied as appropriate from those in the actual device.

As shown in FIG. 4, the elements shown in FIG. 2, such as the drivingtransistor Tdr and the light-emitting element E, are formed on a surfaceof a substrate 10. The substrate 10 is a plate composed at least of aninsulating material, such as glass or plastic. The elements of the unitelement P may be formed on the surface of the substrate 10 using aninsulating film (e.g., a silicon oxide film or a silicon nitride film)covering the substrate 10 as a base. The light-emitting device D in thisembodiment is a top-emission light-emitting device. Thus, the substrate10 does not require optical transparency.

FIGS. 5 to 7 are plan views showing the states on the surface of thesubstrate 10 in different phases of formation of the unit element P. InFIGS. 5 to 7, an area A where the first electrode 21 shown in FIG. 3 isto be formed is indicated by a double-dotted line.

As shown in FIGS. 4 and 5, on the surface of the substrate 10, asemiconductor layer 31 and a semiconductor layer 41 are formed of asemiconductor material, such as silicon. The semiconductor layer 31 andthe semiconductor layer 41 are formed simultaneously in the same processby patterning a film continuously formed over the entire surface of thesubstrate 10. Hereinafter, when a plurality of elements is formedcommonly in the same process by selective removal of a film (regardlessof whether the film is a single-layer film or a multi-layer film), as inthe case of the semiconductor layer 31 and the semiconductor layer 41,the plurality of elements is described as “formed out of the samelayer”. Obviously, the elements formed out of the same layer arecomposed of the same material, and the elements have substantially thesame thicknesses. In a configuration where a plurality of elements isformed out of the same layer, compared with a configuration where theindividual elements are formed out of different layers, advantageously,manufacturing processes can be simplified, and manufacturing cost can bereduced.

As shown in FIGS. 4 and 5, the semiconductor layer 31 includes a firstelement portion 311 and a second element portion 312. The first elementportion 311 is a substantially rectangular portion that functions as asemiconductor layer of the driving transistor Tdr. The second elementportion 312 is a portion that functions as a semiconductor layer of theinitializing transistor Tint. The second element portion 312 includes aportion 312 a extending contiguously from the first element portion 311in the negative Y direction, a portion 312 b extending from the portion312 a in the positive X direction, and a portion 312 c extending fromthe portion 312 b in the positive Y direction.

The semiconductor layer 41 is a portion located on the positive Y sideof the semiconductor layer 31. The semiconductor layer 41 includes theelectrode E2 forming the capacitor C1 shown in FIG. 2, which issubstantially rectangular, and an element portion 411 from the electrodeE2 extending in the positive Y direction. The element portion 411functions as a semiconductor layer of the selecting transistor Ts1.

As shown in FIG. 4, the entire surface of the substrate 10 with thesemiconductor layer 31 and the semiconductor layer 41 formed thereon iscovered with a gate insulating layer L0. As shown in FIGS. 4 and 6, onthe surface of the gate insulating layer L0, the selecting line 11, theinitializing line 12, an intermediate conductor 51, and a firstdata-line portion 131 are formed of a conductive material out of thesame layer.

The selecting line 11 extends in the X direction in association with aplurality of unit elements P, and overlaps the element portion 411 ofthe semiconductor layer 41. In the element portion 411, a regionopposing the selecting line 11 via the gate insulating layer L0 servesas a channel region of the selecting transistor Ts1. The initializingline 12 extends in the X direction in association with a plurality ofunit elements P, and overlaps the second element portion 312 of thesemiconductor layer 31. In the portions 312 a and 312 c of the secondelement portion 312, regions opposing the initializing line 12 via thegate insulating layer L0 serve as channel regions of the initializingtransistor Tint. That is, the initializing transistor Tint in thisembodiment is a dual-gate transistor.

The intermediate conductor 51 is a portion formed in the space betweenthe selecting line 11 and the initializing line 12, and includes theelectrode E1, a gate electrode 511, and a connecting portion 513. Theelectrode E1 is a substantially rectangular region overlapping theelectrode E2 of the semiconductor layer 41 when viewed perpendicularlyto the substrate 10. As shown in FIGS. 4 and 6, the capacitor C1 shownin FIG. 2 is formed of the electrodes E1 and E2 opposing each other viathe gate insulating layer L0 (dielectric layer).

As shown in FIG. 6, the connecting portion 513 extends in the negative Ydirection from an upper right portion of the electrode E1. The gateelectrode 511 extends in the negative X direction from the connectingportion 513 with a gap from the electrode E1, and overlaps the firstelement portion 311 along substantially the entire width (in the Xdirection) of the first element portion 311. As shown in FIG. 4, in thefirst element portion 311, a region opposing the gate electrode 511 viathe gate insulating layer L0 serves as a channel region 311 c of thedriving transistor Tdr. Furthermore, in the first element portion 311, aregion nearer to the electrode E2 than the channel region 311 c (i.e., aregion located in the space between the gate electrode 511 and theelectrode E1 when viewed perpendicularly to the substrate 10 as in FIG.6) serves as a source region 311 s, and a region located opposite to thesource region 311 s with respect to the channel region 311 c serves as adrain region 311 d.

The first data-line portion 131 is a portion constituting the data line13 shown in FIG. 2. The first data-line portion 131 is located on thenegative X side of the intermediate conductor 51, and extends in the Ydirection in the space between the selecting line 11 and theinitializing line 12.

FIG. 8 is a plan view showing four unit elements P in the phase shown inFIG. 6, arrayed in the X and Y directions. As shown in FIGS. 6 and 8, ineach unit element P, the second element portion 312 (the initializingtransistor Tint) formed in a peripheral region on the negative Y side islocated on the positive X side, and the element portion 411 (theselecting transistor Ts1) formed in a peripheral region on the positiveY side is located on the negative X side.

Now, a configuration in which the second element portion 312 and theelement portion 411 are located on the same side in the X direction ineach unit element P will be considered. In this configuration, in orderto separate the second element portion 312 and the element portion 411reliably, sufficient spaces (corresponding to a region B in FIG. 8) mustbe allocated between unit elements P adjacent in the Y direction. Thisinhibits increasing the density of unit elements P. In contrast,according to this embodiment, the second element portion 312 and theelement portion 411 are located on different sides in the X direction ineach unit element P. Thus, the second element portions 312 and theelement portions 411 are located alternately along the X direction inthe region B, as shown in FIG. 8. In this configuration, even when theregion B is narrow, the second element portion 312 and the elementportion 411 are separated reliably. Thus, advantageously, it is readilypossible to increase the density of unit elements P.

As shown in FIG. 4, the entire surface of the gate insulating film L0with the intermediate conductor 51 and the first data-line portion 131formed thereon is covered by a first insulating layer L1. As shown inFIGS. 4 and 7, on the surface of the first insulating layer L1, aconnecting portion 61, a conducting portion 71, the power supply line15, and a second data-line portion 132 are formed of a conductivematerial out of the same layer.

When viewed perpendicularly to the substrate 10 as in FIG. 7, theconnecting portion 61 overlaps the portion 312 c of the second elementportion 312 and the intermediate conductor 51 (the gate electrode 511).The connecting portion 61 is connected to the portion 312 c via acontact hole Ha1 penetrating the first insulating layer L1 and the gateinsulating layer L0. Furthermore, the connecting portion 61 is connectedto the intermediate conductor 51 via a contact hole Ha2 penetrating thefirst insulating layer L1. That is, the gate electrode 511 of thedriving transistor Tdr (the electrode E1 of the capacitor C1) iselectrically connected to the channel region of the initializingtransistor Tint via the connecting portion 61. In this specification, a“contact hole” refers to a portion electrically interconnecting anelement on one side of an insulating layer to an element on the otherside of the insulating layer. More specifically, a contact hole is aportion penetrating an insulating layer in a thickness direction of theinsulating layer. The planar shape of the contact hole may be any shape.

The conducting portion 71 is a portion interposed between the drivingtransistor Tdr and the light-emitting element E and electricallyinterconnecting the driving transistor Tdr and the light-emittingelement E. When viewed perpendicularly to the substrate 10, theconducting portion 71 is located opposite to the capacitor C1 withrespect to the driving transistor Tdr (i.e., on the negative Y side ofthe driving transistor Tdr). In this embodiment, the conducting portion71 has a portion 711 overlapping the drain region 311 d of the firstelement portion 311 and a portion 712 located opposite to the portion711 with respect to the initializing line 12. The portion 711 and theportion 712 are formed contiguously with each other.

Of the first insulating layer L1, in a region overlapping the drainregion 311 d when viewed perpendicularly to the substrate 10, aplurality of contact holes Ha3 penetrating the first insulating layer L1and the gate insulating layer L0 is formed. The contact holes Ha3 arearrayed in the X direction, in which the gate electrode 511 extends(i.e., in the direction of the channel width of the driving transistorTdr). The portion 711 of the conducting portion 71 is connected to thedrain region 311 d via the contact holes Ha3.

FIG. 9 is a plan view showing an array of unit elements P in the phaseshown in FIG. 7. As shown in FIGS. 7 and 9, the power supply line 15 isa strip-shaped line extending in the X direction along an array of aplurality of unit elements P. When viewed perpendicularly to thesubstrate 10, the power supply line 15 overlaps both the capacitor C1and the source region 311 s of the driving transistor Tdr of each unitelement P. As shown in FIGS. 6 and 7, of the first insulating layer L1,in a region overlapping the source region 311 s, a plurality of contactholes Ha4 penetrating the first insulating layer L1 and the gateinsulating layer L0 is formed. The contact holes Ha4 are arrayed in theX direction, in which the gate electrode 511 extends. The power supplyline 15 is connected to the source region 311 s of the drivingtransistor Tdr via the contact holes Ha4. In this embodiment, the shapeand dimensions of the power supply line 15 are chosen so that the powersupply line 15 does not overlap the selecting transistor Ts1 (theelement portion 411), the selecting line 11, the initializing transistorTint (the second element portion 312), or the initializing line 12 whenviewed perpendicularly to the substrate 10. Furthermore, in thisembodiment, the power supply line 15 extends in parallel to theselecting line 11 and the initializing line 12.

The second data-line portion 132 is a portion constituting the data line13 together with the first data-line portion 131. As shown in FIGS. 7and 9, the second data-line portion 132 extends in the Y direction inthe space between a pair of adjacent power supply lines 15. As shown inFIG. 7, an end portion 132 a on the positive Y side (downside) of thesecond data-line portion 132 overlaps an end portion 131 a (refer toFIG. 6) on the negative Y side (upside) of the first data-line portion131 that is adjacent to the positive Y side of the second data-lineportion 132. The end portion 132 a and the end portion 131 a areconnected to each other via a contact hole Ha5 penetrating the firstinsulating layer L1. Similarly, an end portion 132 b on the negative Yside of the second data-line portion 132 and an end portion 131 b (referto FIG. 6) on the positive Y side of the first data-line portion 131that is adjacent to the negative Y side of the second data-line portion132 are connected to each other via a contact hole Ha6. As describedabove, the first data-line portions 131 and the second data-lineportions 132 are arrayed alternately along the Y direction andelectrically connected to each other, forming the data line 13 linearlyextending in the Y direction.

As shown in FIG. 7, a branched portion is formed contiguously with thesecond data-line portion 132. The branched portion 134 is locatedopposite to the capacitor C1 with respect to the selecting line 11. Thebranched portion 134 extends in the X direction and overlaps the elementportion 411 of the semiconductor layer 41. The branched portion 134 iselectrically connected to the element portion 411 via a contact hole Ha7penetrating the first insulating layer L1 and the gate insulating layerL0. That is, the selecting transistor Ts1 is electrically connected tothe data line 13 via the branched portion 134.

As shown in FIG. 4, the entire surface of the first insulating layer L1with the second data-line portion 132 and the power supply line 15formed thereon is covered by a second insulating layer L2. As shown inFIGS. 3 and 4, the first electrode 21 is formed on the surface of thesecond insulating layer L2. The first electrode 21 is formed of alight-reflecting conductive material, for example, a metal such asaluminum or silver, or an alloy mainly composed of one of these metals.The first electrode 21 is electrically connected to the portion 712 ofthe conducting portion 71 via a contact hole Ha8 penetrating the secondinsulating layer L2. That is, the drain region 311 d of the drivingtransistor Tdr is electrically connected to the first electrode 21 ofthe light-emitting element E via the conducting portion 71. Furthermore,when the second insulating layer L2 is formed of an acrylic resin or apolyimide resin, heat is uniformly transferred to the resin via a powersupply line having a high heat conductivity in a process of thermallycuring the resin, so that the resin melts. Thus, the surface of thesecond insulating layer L2 is flattened even further, so that the firstelectrode 21 formed on the second insulating layer L2 becomes flatter.

As shown in FIGS. 3 and 4, when viewed perpendicularly to the substrate10, the first electrode 21 overlaps the conducting portion 71, thedriving transistor Tdr, and the capacitor C1. As shown in FIGS. 6 and 7,the driving transistor Tdr and the capacitor C1 occupy large areas inthe region where the unit element P is formed. Thus, in this embodiment,it is possible to use a large area to form the first electrode 21.Therefore, according to this embodiment, compared with a configurationwhere the first electrode 21 is formed so as to overlap only theselecting transistor Ts1 and the initializing transistor Tint, a highnumerical aperture can be achieved. Furthermore, of the secondinsulating layer L2, on the surface of a region where the firstelectrode 21 overlaps the selecting transistor Ts1 and the initializingtransistor Tint, variation in height could occur reflecting the shapesof these transistors. According to this embodiment, however, the firstelectrode 21 is formed over a large flat surface of the region of thesecond insulating layer L2 overlapping the driving transistor Tdr andthe capacitor C1. Thus, defects (e.g., disconnection) of the firstelectrode 21 or defects of the light-emitting layer 23 due to variationin the height of the second insulating layer L2 can be preventedeffectively.

Furthermore, since the power supply line 15 overlaps the capacitor C1and the source region 311 s of the driving transistor Tdr, as shown inFIGS. 4 and 7, the power supply line 15 exists between the firstelectrode 21 and the source region 311 s of the driving transistor Tdr(and the capacitor C1). In this configuration, compared with aconfiguration where the power supply line 15 does not exist between thefirst electrode 21 and the driving transistor Tdr, capacitive couplingbetween the first electrode 21 and the driving transistor Tdr issuppressed. Thus, the effect of change in the potential of one of thefirst electrode 21 and the driving transistor Tdr on the potential ofthe other is alleviated. This serves to control the light-emittingelement E accurately. Furthermore, since the power supply line 15 isformed so as to cover the driving transistor Tdr and the capacitor C1 inthe region where the first electrode 21 is formed, the surface of thefirst electrode 21 becomes flat.

Furthermore, as shown in FIG. 3, the first electrode 21 overlaps thefirst data-line portion 131 of the data line 13 when viewedperpendicularly to the substrate 10. Since the power supply line 15overlaps the first data-line portion 131, as shown in FIGS. 3 and 7, thepower supply line 15 exists between the first electrode 21 and the firstdata-line portion 131. In this configuration, compared with aconfiguration where the power supply line 15 does not exist between thefirst electrode 21 and the first data-line portion 131, capacitivecoupling between the first electrode 21 and the data line 13 (the firstdata-line portion 131) is suppressed. Thus, the effect of change in thepotential of one of the first electrode 21 and the data line 13 on thepotential of the other is alleviated. This serves to control thelight-emitting element E accurately.

On the surface of the second insulating layer L2 with the firstelectrode 21 formed thereon, a wall 25 is formed of an insulatingmaterial. The wall 25 is an insulating film having an aperture 251 foreach unit element P in association with the first electrode 21. The wall25 serves to electrically insulate adjacent first electrodes 21 fromeach other (i.e., to individually control the potentials of the firstelectrodes 21).

The light-emitting layer 23 is formed contiguously in association with aplurality of unit elements P so as to cover the entirety of the secondinsulating layer L2 with the wall 25 formed thereon. More specifically,the light-emitting layer 23 includes a portion extending inside theaperture 251 and coming into contact with the first electrode 21 (i.e.,a region where light is actually emitted), and a portion located on thesurface of the wall 25. Since the first electrodes 21 are formedindividually for the light-emitting elements E, even though thelight-emitting layer 23 is formed contiguously in association with aplurality of light-emitting elements E, the amount of light emitted bythe light-emitting layer 23 is controlled individually for eachlight-emitting element E. Furthermore, various layers may be laminatedon the light-emitting layer 23 to facilitate or improve the efficiencyof light emission by the light-emitting layer 23, such as a holeinjection layer, a hole transport layer, an electron injection layer, anelectron transport layer, a hole blocking layer, or an electron blockinglayer.

FIG. 11 is a sectional view taken along a line XI-XI in FIG. 3. As shownin FIG. 11, the elements covering the first data-line portion 131 of thedata line 13 (i.e., the first insulating layer L1, the power supply line15, and the second insulating layer L2) exhibit variation in heightreflecting the thickness of the first data-line portion 131. Since thefirst electrode 21 is formed as a thin film on the surface of the secondinsulating layer L2 having such variation in height, of the firstelectrode 21, a region overlapping the data line 13 forms an inclinedsurface 211 reflecting the shape of the first data-line portion 131. Inthis configuration, as indicated by an arrow L in FIG. 11, light emittedfrom the light-emitting layer 23 in a direction parallel to thesubstrate 10 is reflected by the inclined surface 211 so that the lightis directed to the side opposite to the substrate 10 (i.e., to theviewing side). Thus, compared with a configuration where the entiresurface of the first electrode 21 is flat (i.e., a configuration wherelight emitted from the light-emitting layer 23 in a direction parallelto the substrate 10 is not directed to the viewing side), the lightemitted from the light-emitting layer 23 can be used more efficiently.

As shown in FIG. 4, the second electrode 22 is formed contiguously inassociation with a plurality of unit elements P, and covers thelight-emitting layer 23 and the wall 25. Thus, the wall 25 electricallyinsulates the first electrode 21 and the second electrode 22 from eachother in the space between light-emitting elements E. That is, the wall25 defines a region where a current flows between the first electrode 21and the second electrode 22 (i.e., a region where light is actuallyemitted). The second electrode 22 is formed of an optically transparentconductive material, such as indium tin oxide (ITO) or indium zinc oxide(IZO). Thus, light emitted from the light-emitting layer 23 to the sideopposite to the substrate 10 and light emitted from the light-emittinglayer 23 to the side of the substrate 10 and reflected on the surface ofthe first electrode 21 are transmitted through the second electrode 22and output. That is, the light-emitting device D in this embodiment is atop-emission light-emitting device.

Since most optically transparent conductive materials have highresistivities, the second electrode 22 formed of an opticallytransparent conductive material exhibits a high resistance and thereforeexhibits a considerable voltage drop therein along the direction ofcurrent. Thus, voltages individually supplied to the associatedlight-emitting elements E could vary depending on the correspondingpositions in the second electrode 22 along the direction of current.This could cause variation in the amount of light (luminance or tone) inthe light-emitting regions.

In order to suppress the variation in the amount of light, in thisembodiment, an auxiliary line 27 that aids electrical conduction in thesecond electrode 22 is formed. The auxiliary line 27 is formed of aconductive material having a resistivity lower than the resistivity ofthe material of the second electrode 22, and is electrically connectedto the second electrode 22. In FIG. 3, for the purpose of convenience,only the outer shape of the auxiliary line 27 is indicated by adouble-dotted line. FIG. 10 is a plan view showing four unit elements Pin the phase shown in FIG. 3, arrayed in the X and Y directions. Asshown in FIGS. 3 and 10, in this embodiment, when viewed perpendicularlyto the substrate 10, the auxiliary line 27 extends in the X direction inthe space between unit elements P that are adjacent in the Y directionon the surface of the wall 25 (the region other than the apertures 251),and does not overlap the first electrode 21. Furthermore, as shown inFIG. 4, the auxiliary line 27 is located between the light-emittinglayer 23 and the second electrode 22 in contact with the light-emittinglayer 23 and the second electrode 22. In the configuration describedabove, a large portion of current flows through the auxiliary line 27having a lower resistivity, so that the voltage drop in the secondelectrode 22 is reduced. Thus, voltages supplied to the individual unitelements P become uniform, so that variation in the amount of lightamong the individual light-emitting elements E due to the voltage dropcan be alleviated effectively. Although most conductive materials havinglow resistivities, such as the material of the auxiliary line 27, blocklight (or reflect light), in this embodiment, since the auxiliary line27 is formed so as not to overlap the first electrode 21, the numericalaperture is not reduced due to the presence of the auxiliary line 27.

Furthermore, since the auxiliary line 27 does not overlap the drivingtransistor Tdr or the capacitor C1, capacitive coupling between theauxiliary line 27 and the driving transistor Tdr or the capacitor C1 issuppressed. Thus, the effect of change in the potential of one of theauxiliary line 27 and the driving transistor Tdr or the capacitor C1 onthe other is alleviated. This serves to control the luminance of thelight-emitting element E accurately. On the other hand, when viewedperpendicularly to the substrate 10, the auxiliary line 27 overlaps theselecting transistor Ts1 and the initializing transistor Tint as shownin FIGS. 3 and 10. In this embodiment, however, since the wall 25 existsbetween the auxiliary line 27 and the selecting transistor Ts1 or theinitializing transistor Tint (and also the selecting line 11 or theinitializing line 12), compared with a configuration where the wall 25does not exist between the auxiliary line 27 and the selectingtransistor Ts1 or the initializing transistor Tint, capacitive couplingbetween the auxiliary line 27 and the selecting transistor Ts1 or theinitializing transistor Tint is suppressed. Accordingly, in thisembodiment, even though the auxiliary line 27 overlaps the selectingtransistor Ts1 and the initializing transistor Tint, rounding of thewaveform of the selecting signal Sa or the initializing signal Sb issuppressed, so that the selecting transistor Ts1 and the initializingtransistor Tint can operate at a high speed. Although the abovedescription has been given in the context of an example where theauxiliary line 27 is located between the light-emitting layer 23 and thesecond electrode 22, the auxiliary line 27 may be formed on the surfaceof the second electrode 22 (on the surface opposite to thelight-emitting layer 23).

B: Second Embodiment

Next, a specific configuration of a unit element P in a secondembodiment of the invention will be described. The electricalconfiguration of a light-emitting device D in this embodiment is thesame as that in the first embodiment (FIGS. 1 and 2). In the followingdescription, elements corresponding to those in the first embodiment aredesignated by the same signs, and description thereof will be omitted asappropriate.

FIG. 12 is a plan view showing the configuration of a unit element P inthis embodiment. FIGS. 13 to 15 are plan views showing the states on thesurface of the substrate 10 in different phases of formation of the unitelement P shown in FIG. 12. Referring to FIG. 13, on the surface of thesubstrate 10, a semiconductor layer 32, a semiconductor layer 42, and asemiconductor layer 45 are formed of a semiconductor material out of thesame layer. The semiconductor layer 32 is a substantially rectangularregion constituting the driving transistor Tdr. The semiconductor layer42 is a region formed on the positive Y side of the semiconductor layer32. The semiconductor layer 42 includes a substantially rectangularelectrode E2 and an element portion 421 extending in the X directionfrom a lower left portion of the electrode E2. The element portion 421functions as a semiconductor layer of the selecting transistor Ts1. Thesemiconductor layer 45 is a region constituting the initializingtransistor Tint. The semiconductor layer 45 extends in the X directionon the side opposite to the semiconductor layer 32 with respect to thesemiconductor layer 42.

On the surface of the gate insulating layer L0 covering the elementsdescribed above, as shown in FIG. 14, the first data-line portion 131,the selecting line 11, the initializing line 12, an intermediateconductor 52, and a first relaying-line portion 171 are formed out ofthe same layer. The first data-line portion 131 is a portionconstituting the data line 13 as in the first embodiment. The firstdata-line portion 131 extends in the Y direction on the positive X sideof the intermediate conductor 52.

The initializing line 12 has a first gate electrode 121 and a secondgate electrode 122 branching from a portion extending in the X directionto the negative Y side and overlapping the semiconductor layer 45. Inthe semiconductor layer 45, regions respectively overlapping the firstgate electrode 121 and the second gate electrode 122 serve as channelregions of the initializing transistor Tint. Similarly, the selectingline 11 has a first gate electrode 111 and a second gate electrode 112branching from a portion extending in the X direction to the negative Yside and overlapping the element portion 421 of the semiconductor layer42. The first gate electrode 111 and the second gate electrode 112 areadjacent to each other with a gap therebetween. Of the element portion421, regions respectively overlapping the first gate electrode 111 andthe second gate electrode 112 via the gate insulating layer L0 serve aschannel regions of the selecting transistor Ts1. As described above, theselecting transistor Ts1 and the initializing transistor Tint in thisembodiment are dual-gate thin-film transistors.

The intermediate conductor 52 includes an electrode E1 opposing theelectrode E2 to constitute the capacitor C1, a connecting portion 525extending from an upper left portion of the electrode E1 to the negativeY side, a gate electrode 521 extending in the positive X side andoverlapping the semiconductor layer 32, and a connecting portion 523projecting from the substantial center in the X direction of theelectrode E1 to the positive Y side. The gate electrode 521 extends inthe X direction so as to overlap the semiconductor layer 32 along theentire length of the semiconductor layer 32 in the X direction. As shownin FIG. 14, of the semiconductor layer 32, a region opposing the gateelectrode 521 via the gate insulating layer L0 serves as a channelregion 32 c of the driving transistor Tdr. Furthermore, a region on theside of the electrode E1 with respect to the channel region 32 c servesas a source region 32 s, and a region on the opposite side serves as adrain region 32 d.

The first relaying-line portion 171 is a portion constituting a line(hereinafter referred to as a relaying line) for electrically connectingthe initializing transistor Tint to the drain region 32 d of the drivingtransistor Tdr. The first relaying-line portion 171 extends in the Ydirection on the negative X side of the intermediate conductor 52. Thatis, in this embodiment, the intermediate conductor 52 is located betweenthe first data-line portion 131 and the first relaying-line portion 171.

On the surface of the first insulating layer L1 covering the elementsdescribed above, as shown in FIG. 15, the second data-line portion 132,a connecting portion 62, a second relaying-line portion 172, aconducting portion 72, and the power supply line 15 are formed out ofthe same layer.

Similarly to the first embodiment, the second data-line portion 132constitutes the data line 13 together with the first data-line portion131. More specifically, the second data-line portion 132 extends in theY direction from an end portion 132 a to an end portion 132 b. The endportion 132 a is electrically connected via a contact hole Hb1 to anupper end portion 131 a (refer to FIG. 14) of a first data-line portion131 that is adjacent to the positive Y side of the second data-lineportion 132. The end portion 132 b is electrically connected via acontact hole Hb2 to a lower end portion 131 b (refer to FIG. 14) of afirst data-line portion 131 that is adjacent to the negative Y side ofthe second data-line portion 132. Furthermore, in this embodiment, thesecond data-line portion 132 is electrically connected to an end portionof the element portion 421 via a contact hole Hb3 penetrating the firstinsulating layer L1 and the gate insulating layer L0. That is, the dataline 13 is electrically connected to the selecting transistor Ts1 viathe contact hole Hb3.

As shown in FIGS. 14 and 15, the connecting portion 62 extends in the Ydirection so as to overlap the connecting portion 523 of theintermediate conductor 52 and an end portion 451 on the positive X sideof the semiconductor layer 45. The connecting portion 62 is electricallyconnected to the connecting portion 523 via a contact hole Hb4penetrating the first insulating layer L1, and is electrically connectedto the end portion 451 of the semiconductor layer 45 via a contact holeHb5 penetrating the gate insulating layer L0. That is, the electrode E1of the capacitor C1 (and also the gate electrode 521 of the drivingtransistor Tdr) is electrically connected to the initializing transistorTint via the connecting portion 62.

The conducting portion 72 is electrically connected to the firstrelaying-line portion 171 via a contact hole Hb6 penetrating the firstinsulating layer L1. Similarly to the conducting portion 71 in the firstembodiment, the conducting portion 72 is a portion electricallyconnecting the drain electrode of the driving transistor Tdr to thefirst electrode 21 of the light-emitting element E. Of the firstinsulating layer L1, in a region overlapping the drain region 32 d, aplurality of contact holes (two contact holes herein) Hb7 penetratingthe first insulating layer L1 and the gate insulating layer L0 isformed. The contact holes Hb7 are arrayed in the X direction (i.e., inthe direction of the channel width of the driving transistor Tdr), inwhich the gate electrode 521 extends. The conducting portion 72 iselectrically connected to the drain region 32 d via the contact holesHb7.

As shown in FIGS. 14 and 15, the second relaying-line portion 172extends in the Y direction so as to overlap an end portion 452 on thenegative X side of the semiconductor layer 45 and the firstrelaying-line portion 171. The second relaying-line portion 172 iselectrically connected to the end portion 452 via a contact hole Hb8penetrating the first insulating layer L1 and the gate insulating layerL0, and to the first relaying-line portion 171 via a contact hole Hb9penetrating the first insulating layer L1. As described above, theinitializing transistor Tint is electrically connected to the drainregion 32 d of the driving transistor Tdr (and also the connectingportion 72) via a relaying line 17 formed of the first relaying-lineportion 171 and the second relaying-line portion 172.

FIG. 16 is a plan view showing an array of four unit elements P in thephase shown in FIG. 15. As shown in FIGS. 15 and 16, of the firstinsulating layer L1, in a region overlapping the source region 32 (referto FIG. 14) of the semiconductor layer 32, a plurality of contact holes(three contact holes herein) Hb10 penetrating the first insulating layerL1 and the gate insulating layer L0 is formed. The contact holes Hb10are arrayed in the X direction, in which the gate electrode 521 extends.The power supply line 15 is connected to the source region 32 s via thecontact holes Hb10.

In this embodiment, the power supply line 15 has a lattice configurationhaving first portions 151 each extending in the X direction inassociation with a plurality of unit elements P and second portions 152each extending in the Y direction in association with a plurality ofunit elements P. Each of the first portions 151 extends in the Xdirection through the space between a pair of adjacent second data-lineportions 132 and the space between a second relaying-line portion 172and a conducting portion 72 (the portion 721 of the conducting portion72). Thus, when viewed perpendicularly to the substrate 10 as in FIGS.15 and 16, the first portion 151 overlaps the first data-line portion131, the first relaying-line portion 171, and the capacitor C1.Furthermore, each of the second portions 152 extends in the Y directionthrough the space between a conducting portion 72 (the portion 722 ofthe conducting portion 72) and a second data-line portion 132 and thespace between a connecting portion 62 and the second data-line portion132. However, as shown in FIGS. 15 and 16, the second portion 152 doesnot overlap the selecting transistor Ts1 or the initializing transistorTint.

The first electrode 21 shown in FIG. 21 is formed on the surface of thesecond insulating layer L2 with the element described above formedthereon. The first electrode 21 is electrically connected to theconducting portion 72 (and also the drain region 32 d of the drivingtransistor Tdr) via a contact hole Hb11. FIG. 17 is a plan view showingan array of unit elements P in the phase shown in FIG. 12. As shown inFIGS. 12 and 17, the first electrode 21 is formed so as not to overlapthe driving transistor Tdr, the capacitor C1, or the data line 13 (thefirst data-line portion 131). In this configuration, the power supplyline 15 exists between the first electrode 21 and the driving transistorTdr or the capacitor C1, and between the first electrode 21 and thefirst data-line portion 131 of the data line 13. Thus, similarly to thefirst embodiment, capacitive coupling between the first electrode 21 andthe associated elements is suppressed also in this embodiment.

Furthermore, when viewed perpendicularly to the substrate 10 as in FIG.12, in this embodiment, the first electrode 21 does not overlap theselecting transistor Ts1 or the initializing transistor Tint (or theselecting line 11 or the initializing line 12). On the other hand, asshown in FIGS. 12 and 17, the auxiliary line 27 is formed in the spacebetween the first electrodes 21 on the surface of the wall 25 formed onthe surface of the second insulating layer L2, and extends in the Xdirection so as to overlap the selecting transistor Ts1 and theinitializing transistor Tint (and also the selecting line 11 and theinitializing line 12). Since the wall 25 exists between the auxiliaryline 27 and the selecting transistor Ts1 or the initializing transistorTint, similarly to the first embodiment, capacitive coupling between theauxiliary line 27 and the selecting transistor Ts1 or the initializingtransistor Tint is suppressed. The second electrode 22 is configured thesame as in the first embodiment.

From the perspective of merely reducing the resistance of the powersupply line 15 or the first electrode 21 or improving the numericalaperture, the power supply line 15 and the first electrode 21 may beformed so as to overlap the selecting transistor Ts1 and theinitializing transistor Tint as well as the driving transistor Tdr andthe capacitor C1 (this configuration will hereinafter be referred to asa “comparative example”). In the comparative example, however,capacitive coupling could occur between the selecting transistor Ts1 orthe selecting line 11 and the power supply line 15 or the firstelectrode 21 (i.e., a stray capacitance could occur), causing roundingof the waveform of the selecting signal Sa. Similarly, a straycapacitance that occurs between the initializing transistor Tint or theinitializing line 12 and the power supply line 15 or the first electrode21 could cause rounding of the waveform of the initializing signal Sb.Thus, in the comparative example, for example, switching delays couldoccur in the selecting transistor Ts1 or the initializing transistorTint.

In contrast, according to this embodiment, the power supply line 15 andthe first electrode 21 are formed so as not to overlap the selectingtransistor Ts1 or the selecting line 11 and the initializing transistorTint or the initializing line 12. Thus, stray capacitances that occurbetween the power supply line 15 or the first electrode 21 and otherelements are reduced than in the comparative example. Therefore,according to this embodiment, rounding of the waveforms of the selectingsignal Sa and the initializing signal Sb is alleviated, so thathigh-speed operations of the selecting transistor Ts1 and theinitializing transistor Tint are allowed.

C: Third Embodiment

Next, a specific configuration of a light-emitting device D according toa third embodiment of the invention will be described. The embodimentsdescribed above are examples in which all the unit elements are arrangedon the surface of the substrate 10 with the same layout. In contrast, inthis embodiment, the layout of a unit element P differs from the layoutof an adjacent unit element P. The configuration of each unit element Pin this embodiment is the same as that in the second embodiment. Thus,description of the specific configuration of each unit element P will beomitted as appropriate.

FIG. 18 is a plan view showing nine unit elements P in a phase where thefirst data-line portion 131, the selecting line 11, and the initializingline 12 have been formed on the surface of the gate insulating layer L0,the nine unit elements P being arrayed in the X and Y directions. InFIG. 18 and subsequent FIGS. 19 and 20, three columns of unit elements Pon (i−1)-th to (i+1)-th rows are shown. The i-th row is an odd-numberedrow, and the (i−1)-th and (i+1)-th rows are even-numbered rows. As shownin the figures, between the unit elements P on the odd-numbered row(i-th row) and the unit elements P on the even-numbered rows ((i−1)-thand (i+1)-th rows), the layout of elements along the Y direction isopposite.

More specifically, in each of the unit elements P on the even-numberedrows ((i−1)-th and (i+1)-th rows), the selecting transistor Ts1 and theselecting line 11 are located on the positive Y side of the drivingtransistor Tdr (and the capacitor C1 located on the positive Y side ofthe driving transistor Tdr). Furthermore, the initializing transistorTint and the initializing line 12 are located on the positive Y side ofthe selecting line 11. On the other hand, in each of the unit elements Pon the odd-numbered row (i-th row), the selecting transistor Ts1 and theselecting line 11 are located on the negative Y side of the drivingtransistor Tdr (and the capacitor C1 located on the negative Y side ofthe driving transistor Tdr). Furthermore, the initializing transistorTint and the initializing line 12 are located on the negative Y side ofthe selecting line 11. Thus, as shown in FIG. 18, in the space betweeneach pair of a unit element P on the even-numbered row ((i−1)-th row)and a unit element P on the odd-numbered row (i-th row) adjacent theretoon the positive X side, two sets of the selecting line 11 and theinitializing line 12 respectively associated with these unit elements Pexist. On the other hand, in the space between each pair of a unitelement P on the odd-numbered row (i-th row) and a unit element P on theeven-numbered row ((i+1)-th row) adjacent thereto on the positive Yside, the selecting line 11 or the initializing line 12 does not exist.

Of the data line 13, the first data-line portion 131, which is formedout of the same layer as the selecting line 11 and the initializing line12, is formed linearly and contiguously in association with the unitelements P on the odd-numbered row (i-th row) and the unit elements P onthe even-numbered row ((i+1)-th row) adjacent thereto on the positive Yside. That is, the first data-line portion 131 is formed of segments oneither side of the selecting line 11 and the initializing line 12 of theeven-numbered row ((i−1)-th row) and the selecting line 11 and theinitializing line 12 of the odd-numbered row (i-th row) adjacent theretoon the positive Y side.

FIG. 19 is a plan view showing unit elements P in a phase where elements(the second data-line portion 132 and the power supply line 15) havebeen formed on the surface of the first insulating layer L1. As shown inFIG. 19, the second data-line portion 132 is formed so as to cross theselecting line 11 and the initializing line 12 of each of theeven-numbered row ((i−1)-th row) and the odd-numbered row (i-th row)located on the positive Y side. The data line 13 is formed byinterconnecting the first data-line portions 131 adjacent in the Ydirection by the second data-line portions 132. As shown in FIG. 19, thesecond data-line portion 132 extends in the Y direction adjacently to asecond portion 152 of the power supply line 15 formed out of the samelayer.

On the other hand, the first data-line portion 131 is formedcontiguously in association with the odd-numbered row (i-th row) and theeven-numbered row ((i+1)-th row) adjacent thereto on the positive Yside, so that the second data-line portion 132 is not formed in thespace between these rows. Thus, in this embodiment, the width of thesecond portion 152 of the power supply line 15 can be increasedcorrespondingly to the absence of the second data-line portion 132. Thatis, the width of the second portion 152 extending in association withthe odd-numbered row (i-th row) and the even-numbered row ((i+1)-th row)adjacent thereto on the positive Y side is larger than the width Wb ofthe second portion 152 extending in association with the even-numberedrow ((i−1)-th row) and the odd-numbered row (i-th row) adjacent theretoon the positive Y side (Wa>Wb).

FIG. 20 is a plan view showing the state where elements (the firstelectrode 21 and the auxiliary line 27) have been formed on the surfaceof the second insulating layer L2. As shown in FIG. 20, the auxiliaryline 27 formed on the surface of the wall 25 extends in the X directionthrough the space between the first electrodes 21 on the even-numberedrow ((i−1)-th row) and the first electrodes 21 on the odd-numbered row(i-th row) adjacent thereto on the positive Y side, and overlaps theselecting line 11 and the initializing line 12. On the other hand, thefirst electrodes 21 on the odd-numbered row (i-th row) and the firstelectrodes 21 on the even-numbered row ((i+1)-th row) adjacent theretoon the positive Y side are located in proximity to each other, and theauxiliary line 27 does not exist between these electrodes. That is, incontrast to the second embodiment, in which one auxiliary line 27 isformed in association with each row of unit elements P, in thisembodiment, one auxiliary line 27 is formed in association with each setof two rows of unit elements P.

As described above, according to this embodiment, the number of regions(contact holes Hb1 and Hb2) where the first data-line portion 131 iselectrically connected to the second data-line portion 132 can bereduced to about half compared with the second embodiment. Thus,advantageously, the possibility of disconnection of the data line 13(incomplete connection between the first data-line portion 131 and thesecond data-line portion 132) can be reduced. Furthermore, since thewidth of the second portion 152 of the power supply line 15 is increasedin regions where the second data-line portion 132 is not needed, theresistance of the power supply line 15 can be reduced compared with thesecond embodiment. Furthermore, since the auxiliary line 27 is formedwith an increased width so as to overlap the selecting lines 11 and theinitializing lines 12 associated with two rows, the dimensionalprecision required for the auxiliary line 27 is lower than that in thesecond embodiment. Thus, the auxiliary line 27 can be readily formed bylow-cost techniques, such as deposition using a mask.

D: Fourth Embodiment D-1: Electrical Configuration of Light-EmittingDevice

Next, a light-emitting device according to a fourth embodiment of theinvention will be described. FIG. 21 is a circuit diagram showing theelectrical configuration of a unit element P in this embodiment. Asshown in FIG. 21, in the unit element P, the capacitor C1 or theinitializing transistor Tint (the initializing line 12) in theembodiments described above are not formed, and the electricalconnection between the gate electrode of the driving transistor Tdr andthe data line 13 is controlled by the selecting transistor Ts1.Furthermore, a capacitor C2 is provided between the gate electrode andsource electrode (FIG. 15) of the driving transistor Tdr.

In this configuration, when the selecting transistor Ts1 is turned on, adata voltage Vdata corresponding to a tone specified for thelight-emitting element E is supplied from the data line 13 to the gateelectrode of the driving transistor Tdr via the selecting transistorTs1. At this time, charges corresponding to the data voltage Vdata areaccumulated in the capacitor C2. Thus, even when the selectingtransistor Ts1 is turned off, the gate voltage Vg of the drivingtransistor Tdr is maintained at the data voltage Ts1. Accordingly, acurrent corresponding to the gate potential Vg of the driving transistorTdr (a current corresponding to the data voltage Vdata) is continuouslysupplied to the light-emitting element E. With this current supplied tothe light-emitting element E, the light-emitting element E emits lightat a luminance corresponding to the data voltage Vdata.

D-2: Configuration of Unit Element P

Next, a specific configuration of the unit element P in this embodimentwill be described. FIG. 22 is a plan view showing the configuration ofthe unit element P. FIGS. 23 to 25 are plan views showing the states onthe surface of the substrate 10 in different phases of formation of theunit element P. In FIGS. 23 to 25, an area A where the first electrode21 shown in FIG. 22 is to be formed is indicated by a double-dottedline.

As shown in FIG. 23, on the surface of the substrate 10, a semiconductorlayer 34 and a semiconductor layer 44 are formed of a semiconductormaterial out of the same layer. The semiconductor layer 34 is asubstantially rectangular region constituting the driving transistor Tdrand the capacitor C2. The semiconductor layer 44 extends in the Xdirection on the positive Y side of the semiconductor layer 34.

As shown in FIG. 24, on the surface of the gate insulating layer L0covering the semiconductor layer 34 and the semiconductor layer 44, theselecting line 11, the first data-line portion 131, and an intermediateconductor 54 are formed out of the same layer. The selecting line 11 hastwo gate electrodes 114 branching to the negative Y side from a portionextending in the X direction so as to overlap the semiconductor layer44. Regions where the gate electrodes 114 oppose the semiconductor layer44 via the gate insulating layer L0 functions as the dual-gate selectingtransistor Ts1. The first data-line portion 131 is a portionconstituting the data line 13 shown in FIG. 21. The first data-lineportion 131 extends in the Y direction through the space (on thenegative X side of the intermediate conductor 54) between a pair ofselecting lines 11.

The intermediate conductor 54 includes a substantially rectangularelectrode portion F, a connecting portion extending on the negative Yside from the upper left portion of the electrode portion F, and a gateelectrode 541 extending on the positive X side from the connectingportion 545 and overlapping the semiconductor layer 34. A region wherethe electrode portion F and the semiconductor layer 34 oppose each othervia the gate insulating layer L0 functions as the capacitor C2.Furthermore, a region of the semiconductor layer 34 opposing the gateelectrode 541 via the gate insulating layer L0 serves as a channelregion 34 c of the driving transistor Tdr. Furthermore, a region of thesemiconductor layer 34 on the side of the electrode portion F withrespect to the channel region 34 c serves as a source region 34 s, and aregion opposite to the source region 34 s serves as a drain region 34 d.

On the surface of the first insulating layer L1 covering the elementsdescribed above, as shown in FIG. 25, the second data-line portion 132,a connecting portion 64, a conducting portion 74, and the power supplyline 15 are formed out of the same layer. The second data-line portion132 constitutes the data line 13 together with the first data-lineportion 131. The second data-line portion 132 is electrically connectedto the first data-line portion 131 of a row via a contact hole Hc1, andis connected to the first data-line portion 131 of an adjacent row onthe negative Y side via a contact hole Hc2. Furthermore, the seconddata-line portion 132 is electrically connected to the semiconductorlayer 44 via a contact hole Hc3 penetrating the first insulating layerL1 and the gate insulating layer L0.

The connecting portion 64 is a portion electrically interconnecting theselecting transistor Ts1 and the capacitor C2. More specifically, theconnecting portion 64 is electrically connected to the electrode portionF of the intermediate conductor 54 via a contact hole Hc4 penetratingthe first insulating layer L1, and is electrically connected to thesemiconductor layer 44 via a contact hole Hc5 penetrating the firstinsulating layer L1 and the gate insulating layer L0. Furthermore, theconducting portion 74 is a portion electrically connecting the drivingtransistor Tdr to the light-emitting element E. The conducting portion74 is connected to the drain region 34 d of the semiconductor layer 34via a plurality of contact holes Hc6 arrayed in the X direction alongthe gate electrode 541.

FIG. 26 is a plan view showing an array of four unit elements P in thephase shown in FIG. 25. As shown in FIGS. 25 and 26, in this embodiment,the power supply line 15 extends in the X direction in the between eachpair of second data-line portions 132 adjacent in the Y direction. Thepower supply line 15 is electrically connected to the source region 34 sof the semiconductor layer 34 via a plurality of contact holes Hc7penetrating the first insulating layer L1 and the gate insulating layerL0.

The first electrode 21 shown in FIG. 22 is formed on the surface of thesecond insulating layer L2 covering the elements described above. Thefirst electrode 21 is electrically connected to the conducting portion74 via a contact hole Hc8. FIG. 27 is a plan view showing an array offour unit elements P in the phase shown in FIG. 22. As shown in FIGS. 22and 27, the first electrode 21 is formed so as to overlap the drivingtransistor Tdr, the capacitor C2, and the data line 13. In thisconfiguration, since the power supply line 15 exists between the firstelectrode 21 and the driving transistor Tdr or the data line 13,similarly to the first embodiment, capacitive coupling between the firstelectrode 21 and the driving transistor Tdr or the data line 13 issuppressed. Furthermore, since the first electrode 21 does not overlapthe selecting transistor Ts1, capacitive coupling between the firstelectrode 21 and the selecting transistor Ts1 is suppressed.Furthermore, the contact holes Hc1, Hc8, and Hc6 are arrayed linearly inthe X direction, the contact holes Hc1 and Hc4 are arrayed linearly inthe X direction, and the semiconductor layer 44 constituting theselecting transistor Ts1 extends in the X direction. Thus, the powersupply line 15 can extend in the X direction with a relatively largewidth.

On the other hand, as shown in FIGS. 22 and 27, the auxiliary line 27 isformed in the space between the first electrodes 21 on the surface ofthe wall 25 formed on the surface of the second insulating layer L2, andextends in the X direction so as to overlap the selecting transistor Ts1and the selecting line 11. Since the wall 25 is located between theauxiliary line 27 and the selecting transistor Ts1, capacitive couplingbetween the auxiliary line 27 and the selecting transistor Ts1 issuppressed. The layout of the second electrode 22 is the same as that inthe first embodiment.

E: Fifth Embodiment

Next, a fifth embodiment of the invention will be described. In thisembodiment, the layout of a unit element P differs from the layout of aunit element P adjacent thereto in the X direction and the layout of aunit element P adjacent thereto in the Y direction. The configuration ofeach unit element P is the same as that in the fourth embodiment. Thus,description of the specific configuration of each unit element P will beomitted as appropriate.

FIG. 28 is a plan view showing a plurality of unit elements P in thephase where the first data-line portion 131, the selecting line 11, andthe intermediate conductor 54 have been formed out of the same layer,the unit elements P being arrayed in the X and Y directions. In FIG. 28,an i-th row is an odd-numbered row, and (i−1)-th and (i+1)-th rows areeven-numbered rows.

In the configuration shown in FIG. 28, similarly to the thirdembodiment, the layout of elements of the unit elements P is opposite inthe Y direction between the odd-numbered row (i-th row) and theeven-numbered rows ((i−1)-th and (i+1)-th rows). More specifically, ineach of the unit elements P on the odd-numbered row (i-th row), theselecting transistor Ts1 and the selecting line 11 are located on thepositive Y side of the driving transistor Tdr. On the other hand, ineach of the unit elements P on the even-numbered rows ((i−1)-th and(i+1)-th rows), the selecting transistor Ts1 and the selecting line 11are located on the negative Y side of the driving transistor Tdr. Thefirst data-line portion 131 is formed contiguously in association with aunit element P on the even-numbered row ((i−1)-th row) and a unitelement P on the odd-numbered row (i-th row) adjacent thereto on thepositive Y side.

Furthermore, in this embodiment, the layout of the elements of unitelements P is the opposite in the X direction between a j-th column anda (j+1)-th column adjacent in the X direction. More specifically, ineach of the unit elements on the j-th column, the first data-lineportion 131 is located on the positive X side of the driving transistorTdr or the capacitor C2. On the other hand, in each of the unit elementsP on the (j+1)-th column, the first data-line portion 131 is located onthe negative X side of the driving transistor Tdr or the capacitor C2.Thus, the driving transistor Tdr or the capacitor C2 does not exist inthe space between the first data-line portion 131 of the j-th column andthe first data-line portion 131 of the (j+1)-th column.

FIG. 29 is a plan view showing the state where elements (the seconddata-line portion 132 and the power supply line 15) have been formed onthe surface of the first insulating layer L1. As shown in FIG. 29, thesecond data-line portion 132 crosses the selecting line 11 of theodd-numbered row (i-th row) and the selecting line 11 of theeven-numbered row ((i+1)-th row) adjacent thereto on the positive Yside. On the other hand, the second data-line portion 132 is not formedin the space between the even-numbered row ((i−1)-th row) and theodd-numbered row (i-th row) adjacent thereto on the positive Y side.

Furthermore, in this embodiment, in addition to portions extending inthe X direction so as to overlap the capacitors C2 of the unit elementsP, the power supply line 15 includes connecting portions 153interconnecting these portions. Each of the connecting portions 153 isformed in a space between the even-numbered row ((i−1)-th row) and theodd-numbered row (i-th row) adjacent thereto on the positive Y side andoverlapping the first data-line portions 131 of the j-th column and the(j+1)-th column (i.e., a region where the second data-line portion 132is not formed). Thus, according to this embodiment, the area of thepower supply line 15 is increased by the area of the connecting portions153 compared with the fourth embodiment. Accordingly, the resistance ofthe power supply line 15 is reduced, so that variation in thepower-supply potential Vdd at the individual unit elements P can bealleviated.

FIG. 30 is a plan view showing the state where elements (the firstelectrode 21 and the auxiliary line 27) have been formed on the surfaceof the second insulating layer L2. As shown in FIG. 30, the auxiliaryline 27 formed on the surface of the wall 25 extends in the X directionthrough the space between the first electrode of the odd-numbered row(i-th row) and the first electrode 21 of the even-numbered row ((i+1)-throw) adjacent thereto on the positive Y side, and overlaps the selectinglines 11 and the selecting transistors Ts1 of these rows. On the otherhand, the auxiliary line 27 is not formed in the space between theeven-numbered row ((i−1)-th row) and the odd-numbered row (i-th row)(i.e., the region where the selecting line 11 or the selectingtransistor Ts1 is not formed). According to this embodiment, operationand advantage similar to those in the third embodiment can be achieved.

F: Modifications

Various modifications of the embodiments described above are possible.Specific examples of such modifications are described below. Thesemodifications may be implemented in combination as appropriate.

F-1: First Modification

The electrical configuration of the unit element P in the embodimentdescribed above may be modified as appropriate. Specific examples ofmodification of the unit element P will be described below.

(1) As shown in FIG. 31, a transistor (hereinafter referred to as a“light-emission controlling transistor”) Tcnt may be provided betweenthe driving transistor Tdr and the light-emitting element E. Thelight-emission controlling transistor Tcnt is a switching element thatcontrols the electrical connection between the drain electrode of thedriving transistor Tdr and the first electrode 21 of the light-emittingelement E according to a light-emission control signal Sc supplied to alight-emission control line 14. When the light-emission controllingtransistor Tcnt is turned on, a path of a current from the power supplyline 15 to the light-emitting element E is formed, whereby emission oflight by the light-emitting element E is enabled. On the other hand,when the light-emission controlling transistor Tcnt is turned off, thepath is disconnected to disable emission of light by the light-emittingelement E. Thus, it is possible to precisely define a period in whichthe light-emitting element E actually emits light. For example, it ispossible to turn on the light-emission controlling transistor Tcnt sothat the light-emitting element E emits light only in active periods notincluding initializing periods and writing periods. The light-emissioncontrolling transistor Tcnt may be added to the unit element P havingthe configuration shown in FIG. 21.

The layout of the light-emission controlling transistor Tcnt and thelight-emission control line 14 described above may be determinedsimilarly to the example layouts of the selecting transistor Ts1 and theselecting line 11 (or the initializing transistor Tint and theinitializing line 12) according to the embodiments described above.

(2) As shown in FIG. 32, in the example of unit element P shown in FIG.2, the capacitor C2 may be provided between the gate electrode and thesource electrode (the power supply line 15) of the driving transistorTdr. According to this configuration, advantageously, a gate potentialVg of the driving transistor Tdr set in a writing period can bemaintained by the capacitor C2 in a driving period. However, in aconfiguration where a sufficient area is allocated for the gateelectrode of the driving transistor Tdr (i.e., for the channel region),the gate potential Vg is maintained by the gate capacitor of the drivingtransistor Tdr. Thus, it is possible to maintain the gate potential Vgin a driving period even in the configurations according to the first tothird embodiments, where the capacitor C2 is not provided.

As described above, the capacitor connected to the gate electrode of thedriving transistor Tdr may be the capacitor C1 for setting a gatepotential Vg of the driving transistor Tdr by capacitive coupling, orthe capacitor C2 for maintaining a potential of the gate electrode ofthe driving transistor Tdr.

F-2: Second Modification

In the examples described above, the first electrode 21 is composed of alight-reflecting material. Alternatively, the configuration may be suchthat light emitted from the light-emitting layer 23 to the side of thesubstrate 10 is reflected to the side opposite to the substrate 10 by areflecting layer separate from the first electrode 21. In thisconfiguration, a reflecting layer is formed of a light-reflectingmaterial on the surface of the first insulating layer L1, and the firstelectrode 21 is formed so as to cover the reflecting layer. The firstelectrode 21 is formed of an optically transparent conductive material,such as ITO or IZO. Furthermore, although the second electrode 22 isformed of an optically transparent material in the examples describedabove, light emitted from the light-emitting layer 23 can be transmittedeven when the second electrode 22 is implemented by a sufficiently thinelectrode formed of a light-blocking or light-reflecting conductivematerial.

Furthermore, according to the invention, it is also possible toimplement bottom-emission light-emitting devices, in which light emittedfrom the light-emitting layer 23 is output through the substrate 10. Inthis case, for example, the second electrode 22 is formed of alight-reflecting conductive material, and the first electrode 21 isformed of an optically transparent conductive material. In thisconfiguration, light emitted from the light-emitting layer 23 to theside of the substrate 10 and light emitted from the light-emitting layer23 to the side opposite to the substrate 10 and reflected on the surfaceof the second electrode 22 are transmitted through the first electrode21 and the substrate 10 and output.

F-3: Third Modification

In the examples described above, the light-emitting layer 23 is formedcontiguously in association with a plurality of unit elements P.Alternatively, the light-emitting layer 23 may be formed separately inassociation with each unit element P. For example, the configuration maybe such that the light-emitting layer 23 is formed only inside eachaperture defined by the wall 25. Furthermore, the wall 25 may be omittedas appropriate.

F-4: Fourth Modification

In the examples described above, the light-emitting element E includesthe light-emitting layer 23 composed at least of an organic EL material.However, other types of light-emitting elements may be used, such alight-emitting element including a light-emitting layer composed atleast of an inorganic EL material, or a light-emitting diode (LED).According to the invention, it suffices for a light-emitting element toemit light using electric energy (typically a current) supplied thereto,regardless of its specific configuration or material.

G: Example Applications

Next, specific examples of electronic apparatuses including thelight-emitting devices described above will be described. FIG. 33 is aperspective view showing the configuration of a mobile personal computerincluding one of the light-emitting devices D described above. Apersonal computer 2000 includes the light-emitting device D as adisplay, and a main unit 2010. Since the light-emitting device D usesthe light-emitting layer 23 composed of an organic EL material in thelight-emitting element E, it is possible to display an easily viewablescreen with a wide viewing angle.

FIG. 34 shows the configuration of a cellular phone including one of thelight-emitting devices D described above. A cellular phone 3000 has aplurality of operation buttons 3001, scroll buttons 3002, and thelight-emitting device D as a display. By operating the scroll buttons3002, it is possible to scroll a screen displayed on the light-emittingdevice D.

FIG. 35 shows a personal digital assistant (PDA) including one of thelight-emitting devices D described above. A personal digital assistant4000 has a plurality of operation buttons 4001, a power switch 4002, andthe light-emitting device D as a display. When the personal digitalassistant 4000 is powered on by operating the power switch 4002, variousinformation can be displayed on the light-emitting device D, such as anaddress list or a schedule.

As well as the electronic apparatuses shown in FIGS. 33 to 35, examplesof electronic apparatuses that can be implemented using light-emittingdevices according to the invention include digital still cameras, TVsets, video cameras, car navigation devices, pagers, electronicnotebooks, electronic papers, electronic calculators, word processors,workstations, video phones, point-of-sales (POS) terminals, printers,scanners, copying machines, video players, and devices having touchpanels. Furthermore, applications of light-emitting devices according tothe invention are not limited to image display. For example, in an imageforming apparatus such as an optical-writing printer or electroniccopying machine, a write head for exposing a photosensitive membercorrespondingly to an image to be formed on a recording medium such as apaper is used. Such a write head may be implemented using alight-emitting device according to the invention.

1. A light-emitting device comprising: a data line through which a datasignal is supplied; a light-emitting element in which a light-emittinglayer is interposed between a first electrode and a second electrode; apower feeding line through which a predetermined potential is supplied;and a driving transistor that controls a level of a current which flowsthrough the light-emitting element according to the data signal, thedriving transistor being electrically connected between thelight-emitting element and the power feeding line when the current flowsthrough the light-emitting element, the power feeding line including aportion interposed between the first electrode and the data line, andthe portion of the power feeding line overlapping the data line.
 2. Thelight-emitting device according to claim 1, further comprising: aselecting transistor configured to be in an on state or an off stateaccording to a selection signal, and a gate electrode of the drivingtransistor configured to be set at a potential corresponding to the datasignal supplied through the data line and the selecting transistor thathas been in the on state, wherein the first electrode is formed so asnot to overlap the selecting transistor.
 3. An electronic apparatuscomprising the light-emitting device according to claim
 2. 4. Thelight-emitting device according to claim 1, further comprising aninitializing transistor configured to be placed in an on state or an offstate according to an initialization signal, wherein the drivingtransistor is diode-connected through the initializing transistor thatis placed in the on state, and the first electrode is formed so as notto overlap the initializing transistor.
 5. An electronic apparatuscomprising the light-emitting device according to claim
 4. 6. Anelectronic apparatus comprising the light-emitting device according toclaim
 1. 7. The light-emitting device according to claim 1, furthercomprising: a selection line extending in a first direction; and aselecting transistor, a gate of the selecting transistor beingelectrically connected to selection line, the power feeding lineextending in the first direction.
 8. An electronic apparatus comprisingthe light-emitting device according to claim 7.